X-ray photographic equipment

Abstract

An X-ray photographic equipment includes an assembly consisting of an X-ray tube and an X-ray image pickup means with the body of a subject disposed therebetween. The assembly is moved relative to the body of the subject along the direction of a contrast medium flowing in the body of the subject. A plurality of images are obtained every time the assembly is stopped. Video signals representing these images are processed, and a maximum value holding image and a minimum value holding image are found. A difference therebetween represents an image of the blood vessel, which is free from an artefact caused by positional deviation.

We claim: 
     
       1. In an X-ray photographic equipment having image producing means for producing an image signal representing an image of a body of a subject from X-rays passing through the body, said equipment having moving means for producing relative movement between the image producing means and the body of the subject in the direction of flow of a contrast medium through the body, the improvement comprising: control means for stopping said moving means at one of a plurality of positions and, while said moving means is stopped at said one position, repeatedly energizing said image producing means whereby a plurality of image signals each representing an image of said body, are produced;   means responsive to said image producing means for digitizing said image signals to produce frames of digitized image signals representing levels of pixels in said images ranging from black to white;   first frame memory means initially storing a frame image wherein the pixels are all of the black level;   second frame memory means initially storing a frame image wherein the pixels are all of the white level;   means responsive to said control means for comparing, pixel-by-pixel a frame image in said first frame memory means with a frame of digitized image signals and returning to said first frame memory means the pixels which comparison shows to be the whitest, to thereby develop a maximum value holding image;   means responsive to said control means for comparing, pixel-by-pixel, a frame image in said second frame memory means with a frame of digitized image signals and returning to said second frame memory means the pixels which the comparison shows to be the blackest, to thereby develop a minimum value holding image; and,   difference means for determining the difference between said minimum value holding image and said maximum value holding image.   
     
     
       2. The improvement as claimed in claim 1 and further comprising image display means responsive to said difference means for displaying an image. 
     
     
       3. The improvement as claimed in claim 1 wherein said control means includes means for advancing said moving means and stopping it at a second position after the maximum value holding image and the minimum value holding image for said one position have been developed. 
     
     
       4. In an X-ray photographic equipment having image producing means for producing an image signal representing an image of a body of a subject from X-rays passing through the body, said equipment having moving means for producing relative movement between the image producing means and the body of the subject in the direction of flow of a contrast medium through the body, the improvement comprising: control means for stopping said moving means at one of a plurality of positions and, while said moving means is stopped at said one position, repeatedly energizing said image producing means to produce a plurality of image signals each representing an image of said body;   digitizing means for converting each of said image signals into a frame of digital signals representing, pixel-by-pixel, the level of each pixel ranging from black to white;   first means responsive to said digitizing means, for producing signals representing a maximum value holding image wherein each pixel has a level equal to the level of the whitest of the corresponding pixels in each of said frames;   second means, responsive to said digitizing means, for producing signals representing a minimum value holding image wherein each pixel has a level equal to the level of the blackest of the corresponding pixels in each of said frames; and,   difference means, responsive to said first means and said second means for producing difference signals representing the difference between the maximum value holding image and the minimum value holding image.   
     
     
       5. The improvement as claimed in claim 4 wherein said first means comprises a first frame memory and a first comparator, said first comparator having inputs connected to said first frame memory and said digitizing means and an output connected to said first frame memory. 
     
     
       6. The improvement as claimed in claim 5 wherein said first frame memory initially stores signals representing a reference frame wherein each pixel of the reference frame has said black level. 
     
     
       7. The improvement as claimed in claim 5 wherein said second means comprises a second frame memory and a second comparator, said second comparator having inputs connected to said second frame memory and said digitizing means and an output connected to said second frame memory. 
     
     
       8. The improvement as claimed in claim 7 wherein said second frame memory initially stores signals representing a second reference frame wherein each pixel of the second reference frame has said white level. 
     
     
       9. The improvement as claimed in claim 4 and further comprising visual display means responsive to said difference means for visually displaying an image representing the difference between the maximum value holding image and the minimum value holding image. 
     
     
       10. The improvement as claimed in claim 9 wherein said visual display means includes a digital to analog converter connected to said difference means, and a video display connected to said analog to digital converter. 
     
     
       11. An X-ray photographic equipment comprising: X-radiation means;   X-ray image pickup means spaced from said X-radiation means so that a body of a subject may be disposed therebetween,   said X-ray image pickup means facing said X-radiation means so that X-rays produced by said X-radiation means may be received by said X-ray image pickup means after passing through the body of the subject;   means for moving said X-radiation means and said X-ray image pickup means relative to the body of the subject along a direction of flow of a contrast medium in the body of the subject, said moving means including means for stopping said X-radiation means and said X-ray image pickup means at a plurality of positions;   digitizing means responsive to said X-ray image pickup means for producing digital signals representing an image of the body of said subject,   said digital signals representing, for each of a plurality of picture elements comprising said image, a picture element level ranging from black to white;   a first frame memory initially storing a value representing the black level for each picture element of an image; a second frame memory initially storing a value representing the white level for each picture element of an image;   means responsive to said digitizing means for producing, at each position, a maximum value holding image by processing a plurality of images obtained between the time a contrast medium has not reached a position and the time it passes through the position, each of said plurality of images being compared with the first frame memory;   means for producing a minimum holding image, at each position, by processing a second plurality of images, each of said second plurality of images being compared with the second frame memory; and,   means for obtaining a difference between the maximum value holding image and the minimum value holding image.